Add space theme, JSON upload UI, and sample telemetry file

[kavyanshops]

Overview

This pull request adds a CubeSat Mission Control Telemetry Dashboard built with vanilla HTML, CSS, and JavaScript. It visualizes satellite telemetry data (time, temperature, voltage) for a fictional SAST CubeSat and is designed as part of the SAST Technical Team – Software intake assignment 2025.

What this PR does

• Implements a single-page dashboard UI (index.html) with:
  • Live-looking Temperature vs Time and Voltage vs Time line charts using Chart.js.
  • Status cards showing current temperature, voltage, total data points, and mission status (OPERATIONAL / CAUTION).
  • A telemetry data table listing each reading with a status badge (NORMAL / HIGH TEMP / LOW BATTERY).
• Adds support for uploading a JSON telemetry file via:
  • File picker button.
  • Drag & drop on the upload zone.
• Includes:
  • A fallback dataset for demo when no file is uploaded.
  • A “Sample File” download button that generates telemetry_sample.json.
  • A “Clear” button to reset to default/fallback data.